==================================================================
BUG: KCSAN: data-race in _prb_read_valid / data_alloc

write to 0xffffffff86e6e500 of 8 bytes by task 51 on cpu 0:
 data_alloc+0x2fc/0x380 kernel/printk/printk_ringbuffer.c:1129
 prb_reserve+0x8e3/0xaf0 kernel/printk/printk_ringbuffer.c:1727
 vprintk_store+0x54e/0x910 kernel/printk/printk.c:2354
 vprintk_emit+0x1a4/0x610 kernel/printk/printk.c:2455
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2494
 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82
 _printk+0x79/0xa0 kernel/printk/printk.c:2504
 __netdev_printk+0x310/0x370 net/core/dev.c:13148
 netdev_info+0xa6/0xd0 net/core/dev.c:13195
 __dev_set_promiscuity+0x1e5/0x3c0 net/core/dev.c:9672
 __dev_set_rx_mode+0x1e4/0x220 net/core/dev_addr_lists.c:1384
 dev_uc_del+0x145/0x170 net/core/dev_addr_lists.c:845
 vlan_dev_stop+0xcc/0x120 net/8021q/vlan_dev.c:313
 __dev_close_many+0x24d/0x460 net/core/dev.c:1798
 netif_close_many+0x101/0x3a0 net/core/dev.c:1824
 unregister_netdevice_many_notify+0x500/0x1560 net/core/dev.c:12487
 unregister_netdevice_many net/core/dev.c:12589 [inline]
 default_device_exit_batch+0x58c/0x5e0 net/core/dev.c:13288
 ops_exit_list net/core/net_namespace.c:206 [inline]
 ops_undo_list+0x2ca/0x420 net/core/net_namespace.c:253
 cleanup_net+0x37c/0x5b0 net/core/net_namespace.c:706
 process_one_work kernel/workqueue.c:3387 [inline]
 process_scheduled_works+0x56a/0xa50 kernel/workqueue.c:3470
 worker_thread+0x569/0x750 kernel/workqueue.c:3551
 kthread+0x223/0x270 kernel/kthread.c:436
 ret_from_fork+0x146/0x330 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

read to 0xffffffff86e6e500 of 16 bytes by task 2971 on cpu 1:
 desc_read kernel/printk/printk_ringbuffer.c:496 [inline]
 desc_read_finalized_seq kernel/printk/printk_ringbuffer.c:1934 [inline]
 prb_read kernel/printk/printk_ringbuffer.c:1982 [inline]
 _prb_read_valid+0x183/0x930 kernel/printk/printk_ringbuffer.c:2173
 prb_read_valid+0x3c/0x60 kernel/printk/printk_ringbuffer.c:2245
 syslog_print+0x109/0x560 kernel/printk/printk.c:1612
 do_syslog+0x52b/0x7f0 kernel/printk/printk.c:1763
 __do_sys_syslog kernel/printk/printk.c:1855 [inline]
 __se_sys_syslog kernel/printk/printk.c:1853 [inline]
 __x64_sys_syslog+0x41/0x50 kernel/printk/printk.c:1853
 x64_sys_call+0x1d36/0x2550 arch/x86/include/generated/asm/syscalls_64.h:104
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x112/0x360 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 2971 Comm: klogd Not tainted syzkaller #0 PREEMPT(lazy) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
==================================================================